Very Old Curtis Air Compressor Control
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 23
  1. #1
    Join Date
    Feb 2011
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    2,973
    Post Thanks / Like
    Likes (Given)
    2773
    Likes (Received)
    1404

    Default Very Old Curtis Air Compressor Control

    My project to set-up overhead shaft driven machines in my garage is ever changing. I started with a Universal Tool and Cutter Grinder and bench grinder, but I now have a 14" lathe that will be on the same shafting, so my power source is growing. While I'm at it, I found a very old Curtis air compressor that is, you guessed it, flat belt drive. It has a newer Barber Coleman tank and newer motor, so it's really just the compressor head itself that's the jem. I'd like to power it from the same overhead shafting and could use some help.

    The compressor head has two side-by-side flat belt flywheels, one idle and one driven. The original owner says it originally had a hit-n-miss motor to run it and that the operator would manually switch the flat belt on and off of the driven wheel. I'm wondering if there would be a way to automate that process without too much risk or modern technology, and do so mechanically without any electricity. The reason for this is that the overhead shafting is always spinning and without an electric motor that can be easily turned on and off, I need a way to turn off the compressor when the tank gets up to pressure.

    I could do it with a double acting pneumatic cylinder, but each action would need to happen only at the set pressure and not gradually so I'm thinking I need an air activated two way valve with one or two regulators that only let air by at a set PSI.

    The easiest way would of course be to skip the Rube Goldberg show and keep the control in the hands of the operator, I'm just looking at options that would keep it working like a normal compressor.... but mechanically....

  2. #2
    Join Date
    Dec 2010
    Location
    georgia, usa
    Posts
    117
    Post Thanks / Like
    Likes (Given)
    31
    Likes (Received)
    30

    Default

    not rube goldberg at all, you need a pilot valve from a gas compressor and a spring return single acting cylinder. plumb the idle control port of the pilot valve to your cylinder to flip the belt.

    good article by rolair:

    How It Works: Piloted Unloader Valve - Rolair

    as with any compressor be sure your safety valve is tested and in good repair.

  3. Likes M.B. Naegle liked this post
  4. #3
    Join Date
    Dec 2010
    Location
    georgia, usa
    Posts
    117
    Post Thanks / Like
    Likes (Given)
    31
    Likes (Received)
    30

    Default

    use one of these to push the belt over to the free wheel when the pilot trips, the spring will pull it back.

    McMaster-Carr

  5. Likes M.B. Naegle liked this post
  6. #4
    Join Date
    May 2012
    Location
    Pittsford, NY
    Posts
    1,191
    Post Thanks / Like
    Likes (Given)
    837
    Likes (Received)
    836

    Default

    Clutched pulleys on the line shaft were common (Images at line shaft clutched pulley at DuckDuckGo ). While not authentic in terms of a loose pulley, it could be done with minimal modern technology. I think you could use a piloted unloader valve and a spring loaded cylinder on the clutch lever. You'd have to investigate further to be sure.

    I see I type too slowly.

  7. Likes M.B. Naegle liked this post
  8. #5
    Join Date
    Feb 2011
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    2,973
    Post Thanks / Like
    Likes (Given)
    2773
    Likes (Received)
    1404

    Default

    Great! So I'm not crazy! I had been sketching out pneumatic concepts thinking "it shouldn't be this complicated."

    I'll order a piloted unloader valve and we have several pneumatic cylinders that should work for this project. The main motor and overhead shafting is still being put together, so I'm going to use the compressors electric motor to prove the concept first. I imagine that the most complicated parts will be the bracket to hold the cylinder and the belt fork.

    Since there may be little to no pressure to activate the belt control, I'll set-up the cylinder to at rest have the belt on the driven pulley, and at high pressure it will activate the shift the belt off.

    The tank is a horizontal 20 gal. and does have a bit of rust on the bottom with a pin hole in one spot, so I'm looking for a replacement and I will likely use a vertical tank since I don't need a place for a motor. The tank will likely anchor onto the same platform that my tool and cutter grinder sits on.

    I'll get some pictures of everything as it comes together.
    Last edited by M.B. Naegle; 11-18-2020 at 03:15 PM.

  9. #6
    Join Date
    Dec 2010
    Location
    georgia, usa
    Posts
    117
    Post Thanks / Like
    Likes (Given)
    31
    Likes (Received)
    30

    Default

    yep. at zero pressure the belt should be on the driven pulley (the spring in the cylinder or an external spring should have the belt mechanism pulley to that side). Should be simple and reliable. I would possibly have a lever with a catch on the belt shift fork so you can turn the compressor "off" by manually latching the belt over there.

  10. Likes M.B. Naegle, Paolo_MD, dundeeshopnut liked this post
  11. #7
    Join Date
    Feb 2011
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    2,973
    Post Thanks / Like
    Likes (Given)
    2773
    Likes (Received)
    1404

    Default

    For reference, this is the style of valve I'm ordering:
    Gas Air Compressor Pilot Unloader Check Valve Combo 95 - 125 PSI 3/4" X 1/2" 685650074085 | eBay

    It looks like the main variables are the unload pressure, and the connection fittings. 95-125lbs. works for my generic uses, and I take it to mean that the valve will open somewhere within that range (not certain if it's adjustable?), and the valve will be closed at any pressure under the range. This one vents to the atmosphere, which is fine, but I'll probably put an elbow behind the vent since the compressor head will be at chest or head level once it's on a vertical tank and I don't want to blast anyone in the face. I can get smaller/cheaper valves that will likely work fine for this project, but I opted for the 3/4" inlet size as that's what the compressor head measures and I like to avoid adapters where possible.

    How fast do these valves move? If it's more-or-less "instant", I'd like to add an adjustable regulator on the other side of the valve to fine tune the cylinder motion. If it's more of a gradual opening, then perhaps I'm better off with a direct connection.

    Do you think the built in pop-off valve in this combo-assembly is enough, or should I still keep a safety valve on the tank?

    My compressor is also missing the air intake filter. I can always get a modern one, but I found an old intake breather from a hit-n-miss washing machine motor that I think would look better.

  12. #8
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    22,351
    Post Thanks / Like

    Default

    Why shift the belt ?

    Those controls without the cylinder simply open a port upstream of the tank check valve,
    and let the compressor pump with no resistance.

    Much easier & simpler system.

  13. #9
    Join Date
    Feb 2011
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    2,973
    Post Thanks / Like
    Likes (Given)
    2773
    Likes (Received)
    1404

    Default

    Quote Originally Posted by digger doug View Post
    Why shift the belt ?

    Those controls without the cylinder simply open a port upstream of the tank check valve,
    and let the compressor pump with no resistance.

    Much easier & simpler system.
    True, but then the compressor head will be running(/wearing) continuously so long as the shop and overhead shafting is active. My current compressor use is much more on-demand than continuous.

  14. #10
    Join Date
    Mar 2020
    Country
    CANADA
    State/Province
    Quebec
    Posts
    301
    Post Thanks / Like
    Likes (Given)
    500
    Likes (Received)
    186

    Default

    Quote Originally Posted by M.B. Naegle View Post
    For reference, this is the style of valve I'm ordering:
    Gas Air Compressor Pilot Unloader Check Valve Combo 95 - 125 PSI 3/4" X 1/2" 685650074085 | eBay

    It looks like the main variables are the unload pressure, and the connection fittings. 95-125lbs. works for my generic uses, and I take it to mean that the valve will open somewhere within that range (not certain if it's adjustable?), and the valve will be closed at any pressure under the range. This one vents to the atmosphere, which is fine, but I'll probably put an elbow behind the vent since the compressor head will be at chest or head level once it's on a vertical tank and I don't want to blast anyone in the face. I can get smaller/cheaper valves that will likely work fine for this project, but I opted for the 3/4" inlet size as that's what the compressor head measures and I like to avoid adapters where possible.

    How fast do these valves move? If it's more-or-less "instant", I'd like to add an adjustable regulator on the other side of the valve to fine tune the cylinder motion. If it's more of a gradual opening, then perhaps I'm better off with a direct connection.

    Do you think the built in pop-off valve in this combo-assembly is enough, or should I still keep a safety valve on the tank?

    My compressor is also missing the air intake filter. I can always get a modern one, but I found an old intake breather from a hit-n-miss washing machine motor that I think would look better.
    Yes they are instant. All you need inline is a small valve, maybe even a aquarium valve to throttle the cylinder action. Yes to a safety valve as unloaders sometimes stick. Not sure how big your pump is, but if you want a super quiet intake filter/silencer find an old oil bath air cleaner from a tractor. If you don't have intake unloaders for continous running you can keep the oil in it and use that as filtering, mine I have to run empty and use a paper filter on top instead of the cool curved rain cap.001.jpg

  15. Likes M.B. Naegle liked this post
  16. #11
    Join Date
    Feb 2011
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    2,973
    Post Thanks / Like
    Likes (Given)
    2773
    Likes (Received)
    1404

    Default

    Here's pictures of the old Curtis:
    old-curtis-1.jpg
    old-curtis-2.jpg
    old-curtis-3.jpg

    The head's in really good shape (restored in the not to distant past), but I'm not much of a John Deer guy, so I'll likely repaint it at some point to a more neutral grey or black.

    My big hold-up with this project right now, in addition to getting my power source going and overhead works hung, is that I'm having a hard time locating a new tank. The current horizontal tank is approx. 30 gallons, which is perfect for my needs, but everything I'm finding new or used is either way bigger and outside of my budget, or super thin because so many small compressors are portable. I've called several compressor parts companies in the Houston area and none of them sell tanks, or at least tanks this small. The closest vertical tank I've found is in the $800 range + shipping, but it's much bigger than I want.

    Other than being horizontal, my biggest issue with the current tank is that it has a rust pin-hole at the bottom. I'm considering attempting to repair it and while I'm doing that, cutting the legs and top deck off to re-orient it as a vertical tank.... but the safety factor is a big deterrent, especially since this will be indoors in a close quarters shop. I need to re-measure, but I think the tank walls are something between 3/16" and 1/4". It's plenty beefy despite the thinner rust spot in the bottom. IF
    BIG IF
    I did try to fix the tank, the plus side is that with switching orientations, any more standing water that might get left in the tank won't continue eroding the current damage. I would first chemically clean the inside to confirm how extensive the damage is and also hydro-test it after welding before putting it into service, but it's a lot of risk and work that I'm inclined to avoid at the moment and just keep an eye out for something better.

  17. #12
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    22,351
    Post Thanks / Like

    Default

    Quote Originally Posted by M.B. Naegle View Post
    True, but then the compressor head will be running(/wearing) continuously so long as the shop and overhead shafting is active. My current compressor use is much more on-demand than continuous.
    Those compressors can take that long running.
    Your wearing out the entire lineshaft system with all that running anyways.

  18. #13
    Join Date
    May 2020
    Country
    UNITED STATES
    State/Province
    Minnesota
    Posts
    488
    Post Thanks / Like
    Likes (Given)
    194
    Likes (Received)
    189

    Default

    Maybe they can in fact take it. But best not to push one's luck with antiques.

  19. Likes M.B. Naegle liked this post
  20. #14
    Join Date
    Mar 2020
    Country
    CANADA
    State/Province
    Quebec
    Posts
    301
    Post Thanks / Like
    Likes (Given)
    500
    Likes (Received)
    186

    Default

    Don't sell yourself short on your tank. Bigger is always better! You can't have too much air ahead, ESPECIALLY since you are using a lineshaft and a small pump. Good to have enough air on hand to fill a tire or clean a piece of equipment without having to start your lineshaft setup and wait.

  21. #15
    Join Date
    May 2020
    Country
    UNITED STATES
    State/Province
    Minnesota
    Posts
    488
    Post Thanks / Like
    Likes (Given)
    194
    Likes (Received)
    189

    Default

    Along the line of thinking above, also worth considering having your small antique compressor as a 'maintenance' pump used to maintain air pressure in your receiver when doing light operations involving compressed air. E.G. filling tires, using a blow gun, operating an air cylinder infrequently, etc.

    A modern 5-10HP skid/base-mounted pump package set for a lower start-up pressure can then also be plumbed into your receiver as a 'main' pump for high duty jobs that use tons of air. Sand blasting, pneumatic grinders & impact drivers, etc.

    Novelty and convenience at the same time. This will also save your antique from unnecessary wear.

  22. #16
    Join Date
    Nov 2006
    Location
    Bowling Green, Ohio
    Posts
    387
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    156

    Default

    Quote Originally Posted by raven007 View Post
    yep. at zero pressure the belt should be on the driven pulley (the spring in the cylinder or an external spring should have the belt mechanism pulley to that side). Should be simple and reliable. I would possibly have a lever with a catch on the belt shift fork so you can turn the compressor "off" by manually latching the belt over there.
    What happens if the system fails and the belt is not shifted to the idle pulley at the desired pressure? Is there a pop-off safety valve set at a few pounds above the desired pressure to vent the tank so as to eliminate the chance of explosion?

    Bob
    WB8NQW

  23. #17
    Join Date
    May 2020
    Country
    UNITED STATES
    State/Province
    Minnesota
    Posts
    488
    Post Thanks / Like
    Likes (Given)
    194
    Likes (Received)
    189

    Default

    A pressure switch could be fitted to shut down the prime mover driving the line shaft in the event of over-pressure, in addition to the usual safety valves. Being interrupted in the middle of a cut would be annoying, but less so than crashing a machine because a safety valve suddenly popped while you were focused on your work.

  24. #18
    Join Date
    Feb 2011
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    2,973
    Post Thanks / Like
    Likes (Given)
    2773
    Likes (Received)
    1404

    Default

    Quote Originally Posted by blcksmth View Post
    What happens if the system fails and the belt is not shifted to the idle pulley at the desired pressure? Is there a pop-off safety valve set at a few pounds above the desired pressure to vent the tank so as to eliminate the chance of explosion?

    Bob
    WB8NQW
    There's a pop-off valve on the tank, and one built into the unloader valve, but I like Sparky's idea of adding a "kill switch" as well. A 6 volt electrical switch could kill the main power source.

    I mentioned it in a couple other threads related to this line shaft project, but current power source plan is to use a spare 235 Chevy inline 6 (1954 sedan version) with a flat pulley in place of the transmission, clutch still functional, and exhaust and air flow plumbed outside. I'm working on welding together a stand for it right now that will also permit enclosing the motor to keep the air flow and any potential exhaust leaks vented outside, as well as making it quieter. I'm sticking with the stock motor and 6 volt electrical. It might not be as economical as bringing a high voltage line into the garage for an RPC, but I like working on the old GM OHV 6's and it'll provide adequate power for the current machines and any others I drag home in the future. I also have doubts that my little 2 car garage will be the final home of these machines, so the gas engine unit is at least a little more portable than electric.

  25. #19
    Join Date
    Dec 2010
    Location
    georgia, usa
    Posts
    117
    Post Thanks / Like
    Likes (Given)
    31
    Likes (Received)
    30

    Default

    Quote Originally Posted by blcksmth View Post
    What happens if the system fails and the belt is not shifted to the idle pulley at the desired pressure? Is there a pop-off safety valve set at a few pounds above the desired pressure to vent the tank so as to eliminate the chance of explosion?

    Bob
    WB8NQW
    yes of course, there should always be a safety valve of sufficient rating (flow and pressure) to prevent over pressure.

  26. #20
    Join Date
    Dec 2010
    Location
    georgia, usa
    Posts
    117
    Post Thanks / Like
    Likes (Given)
    31
    Likes (Received)
    30

    Default

    Quote Originally Posted by M.B. Naegle View Post
    There's a pop-off valve on the tank, and one built into the unloader valve, but I like Sparky's idea of adding a "kill switch" as well. A 6 volt electrical switch could kill the main power source.

    I mentioned it in a couple other threads related to this line shaft project, but current power source plan is to use a spare 235 Chevy inline 6 (1954 sedan version) with a flat pulley in place of the transmission, clutch still functional, and exhaust and air flow plumbed outside. I'm working on welding together a stand for it right now that will also permit enclosing the motor to keep the air flow and any potential exhaust leaks vented outside, as well as making it quieter. I'm sticking with the stock motor and 6 volt electrical. It might not be as economical as bringing a high voltage line into the garage for an RPC, but I like working on the old GM OHV 6's and it'll provide adequate power for the current machines and any others I drag home in the future. I also have doubts that my little 2 car garage will be the final home of these machines, so the gas engine unit is at least a little more portable than electric.
    You have odd ideas. I like you. What are your plans for a speed governor?

  27. Likes M.B. Naegle liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •